This invention relates to a large, novel, duplex bag construction and to packages formed therewith and particularly, to improved food packages of the type which are suitable for retort and vacuum packaging and which depend upon a metal foil to achieve the necessary barrier properties. Flexible packaging articles useful in retort packaging have been known for some time. They are usually bags formed of laminates of paper or cellophane, one or more thermoplastic plies, and a metal foil ply such as aluminum foil. In general, such packages have been highly successful and continue to improve their share of the market in many packaging applications including packaging of foods wherein the packaged ingredient contains some liquid adding substantially to the weight of the package.
One consideration which must be given to such packaging when more economically desirable flexible sheets are used, is the need to provide protection from the normal abuse that must be expected during transportation over typical rail and truck routes. The problems discussed herein are of particular concern when foil-bearing laminates are used in large pouches, e.g., those having sides of about six inches, or more, or containing over a pound or more of packaged material.
A number of protective measures are known in the packaging art. One is simply to increase the gauge of the sheet materials used to withstand the abuse. In general, however, the cost of such materials has led to the use of other protective procedures. For example, "full folders" have been used wherein the package is fully enclosed in a chip board box or in a four-sided sleeve formed of light cardboard. This is a reasonably successful procedure, but it is expensive also. Use of various cushions has also been tried, these cushions being placed as sheets between the packages as they are packed in cases. Again, the cost is a significant factor and the protection leaves less than is desired.